Sealing wad



T. H. GARBER' SEALING WAD July 19, 1949.

Filed May 31,1945

0 FIG.

. INVENTOR A5 H. @ARER ATTORNEY Patented July 19, 1949 res SEALING WAD 1 Thomas H. Garber, United States Navy, Washingtom. 0.

(Granted under the act ofMarch 3, 1883; as-

amended April 30, 192$; 370 O. G.- 757) This invention. relates to ammunition and has particular relation to' sealing wads for use in cartridge cases. i

The principal purpose of conventional sealing wads is to: provide a moisture protecting means forthe impulsecharges containedin cartridge cases. An additional purpose of sealing wads is to provide separator means between adjacent charges of unlike propellant powders, and they are also usedlas retaining means to. confine impulse powder charges within a given space in a cartridge'case. Conventional sealing wads are ordinarily. composed of combustible material, such as readily ignitable cellulose nitrate, so as to permitcombustion of the sea1ing .wad when. the powder charge isignited. Immediate combustion of'the .sealing wad is essential to protect personnel and equipment in the vicinity from in.- jury caused by flying pieces of the ejected sealing wad which have not been ignited or are not completely b'urned. Conventional sealing wads have the disadvantage that, afterbeing blown fromthe cartridge case, either they are only partially burned'or initial combustion does not take place. These conditions are dangerous not only because the flying particles of sealing wad are injurious to personnel and foul up equipment in the vicinity, but also because the flying particles which are still burning'are a'fire hazard; Furthermore, the flying-particles of sealing wads which arestill burning reveal the location of the firing tothe enemy during battle, particularly at night; Thus, conventional'sealing wads have failed to meet the conditions of-service use either because they do not ignite at all", or because they do'not ignite immediately or do not burn continuously, thereby resulting in incomplete combustion;

An object of this invention is to provide-an ignitable sealing'wadfor use as-a component in cartridge cases" for depth chargeprojector impulse charges, torpedo impulse-charges-and the like;

Another object of the inventionis to. provide, a sealing wad which will burn immediately and completely uponjgnition thereof.

A further objectof the inventionis-. to provide a sealing wad which is of sturdy construction and yet canbe immediately andcompleteiy burned: ina minimum of time.

Still another object-of the invention is-ito :pro: vide .a sealing .wad which occupies aminirn-umof space within a cartridgecase and is economical to manufacture:

These and other obiectsofthe inventiomwill be understood by reference to the accompanying description and drawing, in which Fig. 1 is-a longitudinal sectionalview ofa typical sealing wad of the present invention as positioned inja depth ;charge projector impulse,

charge cartridgecase;

Figs. 2,3, and i areexplodedperspective views partially in section of the elements of the sealing wad shown in Fig; 1; 4

Fig. 5'is a sectional View ofan inner sealing wad for-use in a torpedo impulse charge Fig.6 is a sectional ,viewof a sealing wad having an annular, channel=shaped igniter-portion', and

Fig; 7 is a sectional view of 'a-torpedo impulse chargewithan inner and outersealing wad of th'epresent invention mountedin place.

As shownrinFig. 1, the-sealing wad of the-presentinventionforms a closurecom-ponent for an impulse cartridgercase I0 ordinarily-used in' 'a depthcharge projector. The cartridge case-has a-base- Illa in whichis-secured a primer l I -forignitingapropellant powder charge l2. In-one embodiment, the' sealing wad of the present invention comprises "a cup-shaped member i3-'- having -asubstantially flat base I3a provided with anair release vent I3b having arim l3c;terrni nating in an inturned edge- I3d. Theigniterportion l4 comprises acup-shaped memberof relatively thin" cross=section having a flat base I la provided with-anair release-ventddhcommunicating with-the vent 13b of the sealing wadi cup member. The sides I lc of theigniter'por tion terminate-ins. thin edge- Mdwhichisexposed? to the powder charge l2; A- seal disc I5 is cemented-to the-inner side of the'b'ase l 3a over the vent l3ba-fterassembly of the cha rge as will be hereinafter explained. Forthe purpose" of definition, the igniter'portion'o-f contracted" size in each of its forms assumes an upstanding-re lationship-to tha-t face ofthe'sealing wad which confronts the powder charge. Since it isof a flange or equivalent upstandingformation; as

distinguished from" a coating-on the surface-ofthe-sealing wad; it can'be-defi-ned as a solitaryeminence occupying the aforesaid iface ina solitary-locality. I

In assembling-the charge;- the-desireda-mou-nt of propellant-powder l 2'-is placed-in the cartridge case; The 'igniterportion ld is -cemented-= to the outer baseofthe cup--l3"so*thatthe air release vents [3b and Mb are'in communication. Any suitable cement suchas'nitro cellulosecement may be-utilized-forbonding these elements securely. It will Joe-noticed that the-sides i3c'areslanted at an angle greater than 90 degrees from the base I3a, as shown in Fig. 3, in order to provide secure engagement between the side and the wall of the cartridge case when the sealing wad is inserted therein. The sealing wad is inserted in the cartridge case so that the igniter portion [4 contacts the powder charge I2, the entrapped air being released through the vents I41) and I322. The side of the sealing wad is bonded to the inner cartridge case wall with a waterproofing cement such as 8-1503 manufactured by the Stoner-Mudge Company, Pittsburgh, Pennsylvania, as shown at I6. The seal disc I5 is then cemented to the inner side of the base I3 over the vent l3b, thereby sealing the powder charge within the cartridge case from contact with air, moisture, and foreign matter.

Further modifications of the sealing wads of the present invention are shown in Fig. 6. Referring to Fig, 6, the igniter portion II comprises an annular U-shaped channel of relatively thin cross-sections having a fiat base IM and sides I'Ib terminating in an exposed edge lie. The igniter portion shown in Fig. 6 provides a greater surface of exposed edges than that shown in Figs. 1 and 2. This is of'particular advantage when a small or defective powder charge is used or where the igniter portion is not directly in contact with the powder charge.

Referring now to Fig. 7, there is shown a portion of a torpedo impulse charge having a primer chamber I9, an outer sealing wad 20, and an inner sealing wad 22. The igniter portion of the outer sealing wad is generally similar to that shown in Figs. 1 and 3. inner sealing wad 22, as shown in Fig. 5, has a center opening in the base defined by the inturned flange I3e adapted to fit snugly against the primer chamber I9. The igniter portion comprises an annular cup-shaped flange of relatively thin cross-section. The base of the igniter portion 23 is provided with a central opening adapted to fit snugly about the primer chamber I9. The outer base of the igniter portion is securely cemented to the outer base of the cup 22 so that the upturned edge 23a of the igniter portion is in contact with the powder charge I2 when the sealing wad is inserted in the cartridge case over the primer chamber. When the igniter (not shown) is fired, it ignites the powder charge I2 through the vents I9b communicating with the chamber I911. The upturned edge 23a, which is in contact with the burning powder I2, immediately initiates combustion of the sealing wad as it is blown from the cartridge case. the flame from the igniter passes along the chamber I9a contacting the igniter portion of the outer sealing wad and the igniter portion thereof immediately initiates combustion of the outer sealing wad.

It is apparent that the ignition of the sealing wad must be instantaneous with the combustion of the powder charge caused by the ignition of the igniter. If instantaneous burning of the sealing wad does not take place, the wad will be blown from the cartridge case without having been ignited or ignition thereof will take place after the wad has been projected from the case. Either of the aforementioned conditions is unsatisfactory due to the danger of flying particles, either burning or unburned, which are projected from the case.

In order to provide instantaneous, continuous and complete burning of the sealing wad, it has been found that the cross-sectional width of the The main body of the :2.

A portion of cup member, and particularly of the igniter portion, must be held within critical limits. Thus, it has been found that the thickness of the cup member of the sealing wad must be no greater than approximately 0.05 inch in order to provide continuous and complete burning thereof. It has also been found that the thickness of the igniter portion edge should be approximately 0.01 inch although igniter portions having an edge thickness of not less than 0.008 inch nor more than 0.02 inch have been successfully used. The thickness of the seal disc is preferably approximately 0.03 inch. It has been found that if the thickness of the igniter portion edge is substantially less than 0.01 inch, continuous burning cannot be obtained; whereas, if the thickness is substantially greater than 0.01 inch, instantaneous ignition cannot be efiected.

The sealing wad of the present invention is preferably composed of Celluloid or Pyralin, preferably a homogeneous nitro cellulose camphor compound. One composition which has proven particularly satisfactory is composed of approximately three parts nitro cellulose, approximately one part camphor, plus about .75% of the dry weight of nitro cellulose of urea, said components being dissolved in a suitable solvent. The nitro cellulose used is preferably prepared from cotton cellulose. It should have a nitrogen content of approximately 11% and should be at least 99% soluble in acetone and it should have a purification treatment of at least eight hours boiling at 100 degrees C. in acid water with an equivalent acid content equal to at least 05% sulfuric acid. The camphor used should be of such qua1 ity that a 20 gram sample, heated in a glass cup for four hours in a suitable oil bath at degrees C., should show no discoloration. The urea should be neutral or very slightly alkaline and free from ammoniacal odor. The finished nitro cellulose should have a melting point of approximately 132 degrees C.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cup shaped member having a substantially fiat base provided with a solitary eminence on one side of said base, of contracted size relative to the size of the base to constitute an ignition portion for initiating combustion of the sealing wad.

2. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cup shaped member having a substantially fiat base, and an igniter portion of relatively thin crosssection mounted on and projecting from the outer side of said base, said igniter portion being of contracted size as compared with the size of said base and therefore constituting a. solitary eminence which is adapted to be packed in a contiguous powder charge for initiating combustion of the sealing wad from within the confines of said base when the powder charge is burned.

3. Means as set forth in claim 2 in which said igniter portion comprises at least one fin-shaped projection of relatively thin cross-section lo cated medially of the boundary of said base and projecting from said base as a solitary eminence for initiating combustion of the sealing wad.

4. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cupshaped member having a substantially flat base and an igniter portion comprising at least one fin-shaped circular projection of relatively thin cross-section mounted on and projecting from the outer side of said base for initiating combustion of the sealing wad.

5. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cupshaped member having a substantially fiat base provided with an aperture and an igniter portion of relatively thin cross-section mounted on and having an aperture registering with the aperture in the base, said igniter portion projecting from the outer side of said base for initiating combustion of the sealing wad.

6. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cupshaped member having a substantially flat base and an igniter portion comprising a cup-shaped element of relatively thin cross-section having a substantially flat base, the outer side of said igniter portion being mounted onto the outer side of the base of said sealing wad, and the side of said igniter portion projecting away from the base of the sealing wad for initiating combustion of said sealing wad.

7. An ignitable and combustible sealing wad for use in a cartridge case, comprising a cupshaped member having a substantially fiat base and an igniter portion comprising an annular channel of relatively thin cross-section, the outer side of said igniter portion being mounted onto the outer side of the base of said sealing wad and the sides of said channel projecting away from the base for initiating combustion of said sealing wad.

8. A sealing wad for use in a cartridge as a powder charge follower, comprising a combustible closuremember adapted to be thrust into said case with one of its faces confronting the powder charge, and an igniter portion centered on said face, being spaced in from the boundary of and upstanding from said face in flange formation, said portion having a thin edge exposed to said powder charge.

THOMAS H. GARBER.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,068,159 Frantzious Jan. 19, 1937 2,299,465 Coifman Oct. 20, 1942 2,362,927 Pratt Nov. 14, 1944 2,366,165 Whitworth Jan. 2, 1945 FOREIGN PATENTS Number Country Date 271,390 Great Britain May 26, 1927 

